The Hymeks were intended as a medium power mixed traffic loco, but were often rostered to deputise for some of the WR's largest steam locos on 13 and 14-coach trains in their early years. 101 locos were built up to 1964 and allocated all over the Western Region. They settled down to become a successful and capable fleet.

Introduced in 1961-4 the Hymeks careers were cut short by BR's standardisation with diesel electric types. The first withdrawals came in 1971, with some locos scrapped being less than nine years old. Full withdrawal of the fleet was planned for 1973, and a farewell tour, The Hymek Swansong, ran in September. Due to loco shortages, ten Hymeks soldiered on to 1975 when they were finally withdrawn. Of these, four have survived into preservation, our two - D7017 and D7018, D7029 with the Diesel Traction Group, and D7076 with the Bury Hydraulic Group.